RE: PD modeling of dataset with opposite values in the measurement effect

From: Gibiansky, Katya Subject: RE: [NMusers] PD modeling of dataset with opposite values in the measurement effect Date: Wednesday, January 25, 2006 3:28 PM Liping, A couple of notes. First, increase in blood pressure compared to baseline is likely due to variability of baseline and not due to the drug. In the absence of any drug effect and some systematic change (e.g. circadian variation), one would expect 50% of PD data points to go up and 50% to go down compared to baseline. To cope with the negative effect, you need to account for baseline variability (i.e. estimate it and use estimated population+individual values in the model rather than the observed value). Second, if it is not a variability or some systematic difference in the measurements issue, and you want to correlate it with the drug concentrations, there is no rational why the correlation should be described by the same relationship for those who respond negatively and positively to the drug. Katya _______________________________________________________